A WhatsApp registration code is a 6-digit code that is sent to your phone via SMS or phone call when you create a new account or re-register an existing account. You must enter this code to confirm that you own the phone number and activate your account. It is important to note that you should never share your registration code with anyone, as it is a crucial security feature that helps protect your account from being hijacked. If you receive a verification code without requesting it, it could mean that someone is attempting to register a WhatsApp account with your phone number. In this case, you should not share the code with anyone and report the incident to WhatsApp to keep your account safe.